docs: def com_google_fonts_check_all_glyphs_have_codepoints(ttFont):
    """Check all glyphs have codepoints assigned."""
    failed = False
    for subtable in ttFont['cmap'].tables:
      if subtable.isUnicode():
        for item in subtable.cmap.items():
          codepoint = item[0]
          if codepoint is None:
            failed = True
            yield FAIL, ("Glyph {} lacks a unicode"
                         " codepoint assignment").format(codepoint)
    if not failed:
      yield PASS, "All glyphs have a codepoint value assigned."